How authentic is the story of the 'awrah of Amr ibn al-'As, when Ali (may Allah be pleased with him) uncovered it, causing Ali to turn his face away from him?

The mentioned report is false and not supported by any chain of transmission. It has been narrated in several sources from Nasr ibn Muzahim, who is a weak Shiite narrator, and from Ibrahim al-Bayhaqi, who is unknown, and from Sibt ibn al-Jawzi, who is a weak Rafidhi (Shiite). Therefore, the story is denounced in terms of its chain of narration and its text; it was fabricated by the Shiites, and it is not permissible to disseminate it.